Liquid ink printers of the type frequently referred to as continuous stream or as drop-on-demand, such as piezoelectric, acoustic, phase change wax-based or thermal, have at least one printhead from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in a plurality of channels. Power pulses cause the droplets of ink to be expelled as required from orifices or nozzles at the end of the channels.
In a thermal ink-jet printer, the power pulse is usually produced by a heater transducer or a resistor, typically associated with one of the channels. Each resistor is individually addressable to heat and vaporize ink in the channels. As voltage is applied across a selected resistor, a vapor bubble grows in the associated channel and initially bulges from the channel orifice followed by collapse of the bubble. The ink within the channel then retracts and separates from the bulging ink thereby forming a droplet moving in a direction away from the channel orifice and towards the recording medium whereupon hitting the recording medium a drop or spot of ink is deposited. The channel is then refilled by capillary action, which, in turn, draws ink from a supply container of liquid ink.
The ink jet printhead may be incorporated into either a carriage type printer, a partial width array type printer, or a page-width type printer. The carriage type printer typically has a relatively small printhead containing the ink channels and nozzles. The printhead can be sealingly attached to a disposable ink supply cartridge. The combined printhead and cartridge assembly is attached to a carriage which is reciprocated to print one swath of information (having a height equal to the length of a column of nozzles), at a time, on a stationary recording medium, such as paper or a transparency. After the swath is printed, the paper is stepped a distance equal to the height of the printed swath or a portion thereof, so that the next printed swath is contiguous or overlapping therewith. This procedure is repeated until the entire page is printed. In contrast, the page width printer includes a stationary printhead having a length sufficient to print across the width or length of a sheet of recording medium at a time. The recording medium is continually moved past the page width printhead in a direction substantially normal to the printhead length and at a constant or varying speed during the printing process. A page width ink-jet printer is described, for instance, in U.S. Pat. No. 5,192,959.
Various printers and methods are illustrated and described in the following disclosures which may be relevant to certain aspects of the present invention.
In U.S. Pat. No. 4,748,453 to Lin et al., a method of depositing spots of liquid ink on a substrate is described. A line of information is printed in at least two passes so as to deposit spots of liquid ink on selected pixel centers in a checkerboard pattern wherein only diagonally adjacent pixel areas are deposited in the same pass.
U.S. Pat. No. 5,057,854 to Pond et al. describes modular partial bars and full width array printheads fabricated from modular partial bars. The modular partial bars include a substrate bar having a length and a plurality of printhead subunits attached to only one side of the substrate bar. The modular partial bars are used as building blocks to form full width staggered array printheads.
U.S. Pat. No. 5,160,945 to Drake describes a page width thermal ink jet printhead for an ink jet printer. The printhead is of the type assembled from fully functional roof shooter type printhead subunits.
U.S. Pat. No. 5,216,442 to Parks et al. describes an ink jet printer having a platen with a planar surface sized to hold a sheet. The platen is movably mounted for linear reciprocal movement between a sheet receiving position and a sheet releasing position.
U.S. Pat. No. 5,300,957 to Burke describes a method and apparatus for high speed interlaced printing in the direction of printhead scanning. A cylindrical drum is rotatable about a drum axis for supporting a print medium during printing. The drum is rotated about the drum axis at a predetermined speed such that alternate image-element locations are addressed by each printing element during each rotation of the drum at the predetermined rate. The drum rotates two revolutions at each printhead location along with access and all image element locations are addressed.
U.S. Pat. No. 5,572,244 to Drake et al. describes a large array or page width printhead fabricated from printhead elements or subunits having adhesivefree butting edges. Each of the printhead elements includes a heater element and a channel element bonded together by an adhesive such as an epoxy.
U.S. Pat. No. 5,541,625 to Holstun et al. and U.S. Pat. No. 5,600,351 to Holstun et al. describe an ink jet printer system which fires smaller ink droplet in a single pass print mode to achieve a print resolution of 600 dpi in the carriage scan axis along with 300 dpi resolution in the media advance axis.